Conventional marker navigation systems, in particular so-called image-guided surgery (IGS) systems, generally detect and track the locations of one or more reference frames that, for example, are connected to a body structure (e.g., a bone) or to an instrument. A display of a marker navigation system typically shows only a particular region or section (e.g., a targeted region) of the operating area.
One problem with conventional marker navigation systems is that if a change occurs in the targeted region, it may be unclear whether the change was due to camera movement or to movement of the observed marker means (which for example may be connected to a body structure or an instrument).
Another problem is that large relative movements of the marker means can occur such that the objects connected to the respective marker means (e.g., the body structure or instrument), which are typically calibrated, are no longer displayed on the display (e.g., they have moved out of a display region and are “off the display”). The latter may be due to the fact that while a camera system, for example, detects a general region (e.g., the patients upper body), the surgeon may be only interested in a sub-region (e.g., a portion of the patient's chest) of the general region, and only this sub-region is displayed of the display. Thus, if the displayed objects of interest leave the sub-region (e.g., they move outside the display area), the surgeon may prefer that the display area be re-adjusted such that the objects of interest are again provided on the display.